JP2017213926A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can improve uneven wear resistance performance and travelling performance on a muddy road surface, and can make both performance compatible with good balance.SOLUTION: In the pneumatic tire, in a shoulder region are alternately provided along a tire circumferential direction a plurality of first lug grooves 11 and a plurality of second lug grooves 12 shorter than the first lug grooves, and are provided a first connecting groove 21 connecting tip parts of the first lug grooves to the second lug grooves and a second connecting groove 22 connecting tip parts of the second lug grooves to the first lug grooves. An angle θ1 of the first connecting groove is set larger than an angle θ2 of the second connecting groove. End parts inside in a tire width direction of first shoulder blocks 31 partitioned by the first lug grooves, the second lug groove and the first connecting groove are arranged closer to a tire equator CL side than the end parts inside in the tire width direction of second shoulder blocks 32 partitioned by the first lug grooves, the second lug groove and the second connecting groove. In the first and the second shoulder blocks are provided respectively transverse grooves 31a and 32a crossing the blocks.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that improves uneven wear resistance and running performance on a muddy road surface, and makes it possible to balance these performances in a well-balanced manner.

  In general, a pneumatic tire used for traveling in a muddy area, a snowy road, a sandy land (hereinafter referred to as a muddy area) has a tread pattern mainly composed of lug grooves and blocks having a lot of edge components. A thing with a large area is adopted. In such tires, mud, snow, sand, etc. (hereinafter referred to as mud) on the road surface is bitten to obtain traction performance, and mud etc. is prevented from clogging in the groove (improving mud discharge performance) The traveling performance (mud performance) in a muddy area is improved (see, for example, Patent Document 1).

  However, a tread pattern mainly composed of such blocks tends to cause uneven wear. In particular, when the groove area is increased to improve the mud performance, the block rigidity is lowered, so that the uneven wear resistance performance is lowered, and it is difficult to achieve both the mud performance and the uneven wear resistance performance. . For this reason, there is a demand for measures to improve both the mud performance and the uneven wear resistance even in the case of a pattern mainly composed of blocks and to balance both in a balanced manner.

Japanese Patent No. 4537799

  An object of the present invention is to provide a pneumatic tire that improves uneven wear resistance and running performance on a muddy road surface, and makes it possible to balance these performances in a balanced manner.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A plurality of first lug grooves extending in the tire width direction in the shoulder region of the tread portion and the first lug grooves, A plurality of short second lug grooves, the first lug grooves and the second lug grooves are alternately arranged along the tire circumferential direction, from the tip of the first lug groove to the second lug groove An extending first connecting groove and a second connecting groove extending from the tip of the second lug groove to the first lug groove, and an angle of the first connecting groove with respect to a tire circumferential direction is the second The angle of the connecting groove with respect to the tire circumferential direction A plurality of first shoulder blocks are defined by the first lug groove, the second lug groove, and the first connection groove, and the first lug groove, the second lug groove, and the first lug groove A plurality of second shoulder blocks are defined by the two connecting grooves, and the inner end portion in the tire width direction of the first shoulder block is disposed closer to the tire equator than the inner end portion in the tire width direction of the second shoulder block. Each of the one shoulder block and the second shoulder block includes a transverse groove that crosses each block while being inclined with respect to the tire circumferential direction.

  In the present invention, as described above, the first lug groove, the second lug groove, the first connection groove, and the second connection groove are provided, and the first shoulder block and the second shoulder block are partitioned by these. In addition, the mud performance for efficiently discharging the mud in the groove can be enhanced while the mud etc. are well bitten to obtain excellent traction performance, and the mud performance can be improved. In particular, since the angle of the first connecting groove with respect to the tire circumferential direction is larger than the angle of the second connecting groove with respect to the tire circumferential direction as described above, the traction performance is relatively shorter than the first lug groove. The traction performance of the low second lug groove can be supplemented by the first connection groove, and the drainage performance of the first lug groove, which is longer than the second lug groove and is relatively low in mud drainage performance, is improved by the second connection groove. Can be supplemented, and the mud performance can be effectively enhanced. On the other hand, each of the first shoulder block and the second shoulder block is provided with a transverse groove, so that the first shoulder block and the second shoulder block are appropriately divided to suppress the rigidity difference between these blocks. It is possible to improve uneven wear resistance.

  In the present invention, it is preferable that the transverse groove is disposed at a position where the distance from the outer edge in the tire width direction of each block is the same in the first shoulder block and the second shoulder block. By arranging the transverse grooves in this way, the rigidity of the outer portion in the tire width direction defined by the transverse grooves of the first shoulder block and the second shoulder block can be made substantially uniform, and the uneven wear resistance is improved. Is advantageous.

  At this time, it is preferable that the first shoulder block has a neck portion at the ground contact end position, and the edge of the first shoulder block on the outer side in the tire width direction is located on the inner side in the tire width direction than the ground contact end position. Thus, in order to make the positions of the transverse grooves in the first shoulder block and the second shoulder block the same distance from the outer edge in the tire width direction of each block, the transverse grooves formed in the blocks adjacent to each other in the tire circumferential direction. This is advantageous for improving the uneven wear resistance by improving the balance of block rigidity.

  In this invention, it is preferable that the angle with respect to the tire circumferential direction in the ground contact end position of a 1st lug groove and a said 2nd lug groove is 60-90 degrees at an acute angle side, respectively. By setting the angle of each lug groove in this manner, the traction performance in the shoulder region can be improved, which is advantageous for improving the mud performance.

  In the present invention, a plurality of third connection grooves that connect the first connection grooves located on both sides of the tire equator and a plurality of fourth connection grooves that connect the second connection grooves located on both sides of the tire equator; It is preferable that a plurality of center blocks are defined on the tire equator by the first connection groove, the second connection groove, the third connection groove, and the fourth connection groove. Thereby, the traction performance by the third connection groove and the fourth connection groove can be ensured in the center region, which is advantageous for improving the mud performance.

  At this time, it is preferable that the angle of the third connection groove with respect to the tire circumferential direction is smaller than the angle of the fourth connection groove with respect to the tire circumferential direction. This improves drainage performance for the third connection groove connected to the first connection groove with excellent traction performance, and improves traction performance for the loud connection groove connected to the second connection groove with excellent drainage performance. Since it can improve, it becomes possible to exhibit a mud performance highly by the combination of these 1st-4th connection grooves.

  In the present invention, the center block preferably includes a center sipe extending along the second connecting groove. As a result, the rigidity of the center block, which tends to be high in rigidity because it is located on the extended line of the second lug groove with a short groove length, is suppressed, and the difference in block rigidity between the second lug groove and the second connecting groove is suppressed. Thus, uneven wear resistance can be improved. Moreover, since the edge effect by sipe can be expected, the traction performance can also be improved.

  At this time, the first shoulder block includes a first shoulder sipe extending along the second lug groove, the second shoulder block includes a second shoulder sipe extending along the second lug groove, the center sipe, and the first shoulder sipe. It is preferable that the second shoulder sipe is arranged so as to surround the second lug groove as a series of sipes. Thereby, the rigidity balance of the first shoulder block, the second shoulder block, and the center block, in particular, the peripheral edge portion of the second lug groove can be improved, which is advantageous for improving the uneven wear resistance. Moreover, since the edge effect by sipe can be expected, it is advantageous for improving the traction performance.

  In the present invention, the ground contact end is an end portion in the tire axial direction when a normal load is applied by placing the tire on a normal rim and filling the normal internal pressure vertically on a plane. A region between the ground contact ends on both sides in the tire width direction is referred to as a “ground contact region”. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORMATION PRESURES”, “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the load.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a front view which shows the tread surface of the pneumatic tire which consists of embodiment of this invention. It is a principal part enlarged view which shows the 1st and 2nd shoulder block of FIG. It is explanatory drawing shown about arrangement | positioning of a transverse groove. It is a principal part enlarged view which shows the center block of FIG.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the pneumatic tire of the present invention includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction. In addition, in FIG. 1, the code | symbol CL shows a tire equator and the code | symbol E shows a grounding end.

  A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. Further, a plurality of layers (two layers in FIG. 1) of belt reinforcement layers 8 are provided on the outer peripheral side of the belt layer 7. The belt reinforcing layer 8 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

  As shown in FIGS. 2 and 3, the tread portion 1 includes a first lug groove 11, a second lug groove 12, a first connection groove 21, a second connection groove 22, a third connection groove 23, and a fourth connection groove 24. Are provided in plurality. In addition, a plurality of first shoulder blocks 31, second shoulder blocks 32, and center blocks 34 are partitioned by these grooves. The third connecting groove 23 and the fourth connecting groove 24 and the center block 34 defined by a plurality of grooves including the third connecting groove 23 and the fourth connecting groove 24 are optional elements as will be described later. It is not always necessary to provide it.

  The first lug groove 11 is a groove extending in the tire width direction in the shoulder region (region outside the tire width direction) of the tread portion 1. In the illustrated example, the shoulder region extends substantially in the tire width direction, and in the center region, the inclination angle with respect to the tire width direction gradually increases toward the tire equator CL side. The first lug groove 11 has a groove length larger than that of the second lug groove 12 described later, and in the illustrated example, one end opens toward the outer side in the tire width direction beyond the ground contact end E, and the other end is the tire equator. It reaches CL and terminates. In the illustrated example, a protruding portion 11 a that protrudes from the groove bottom and extends along the first lug groove 11 is formed at the center of the groove bottom near the ground contact E of the first lug groove 11.

  Similar to the first lug groove 11, the second lug groove 12 is a groove extending in the tire width direction in the shoulder region (outer region in the tire width direction) of the tread portion 1. In the illustrated example, the shoulder region extends substantially in the tire width direction, and in the center region, the inclination angle with respect to the tire width direction gradually increases toward the tire equator CL side. The second lug groove 12 is shorter than the first lug groove 11 described above, and in the illustrated example, one end terminates in a side block 33 disposed at a position beyond the ground contact E, and the other end. Terminates at a position outside the tire equator CL in the tire width direction. In the illustrated example, a protruding portion 12 a that protrudes from the groove bottom and extends along the second lug groove 12 at the center of the groove bottom near the ground contact E of the second lug groove 12 is formed.

  These first lug grooves 11 and second lug grooves 12 are alternately arranged along the tire circumferential direction. A first connection groove 21 and a second connection groove 22 are formed between the first lug groove 11 and the second lug groove 12 that are adjacent to each other in the tire circumferential direction.

  The first connection groove 21 is a groove extending from the tip end portion of the first lug groove 11 to the second lug groove 12. At this time, the connection position of the first connection groove 21 with respect to the second lug groove 12 is not particularly limited. In the illustrated example, the first connection groove 21 is connected to the tip of the second lug groove 12. The first connecting groove 21 extends in an inclined manner with respect to the tire circumferential direction, depending on the positional relationship between the first lug groove 11 and the second lug groove 12. However, the angle θ1 of the first connecting groove 21 with respect to the tire circumferential direction is set larger than the angle θ2 of the second connecting groove 22 described later with respect to the tire circumferential direction.

  The second connecting groove 22 is a groove extending from the tip of the second lug groove 12 to the first lug groove 11. At this time, the connection position of the second connection groove 22 with respect to the first lug groove 11 is not particularly limited. In the illustrated example, the second connection groove 22 is connected to the middle part of the first lug groove 11. Although the 2nd connection groove | channel 22 depends on the positional relationship of the 1st lug groove 11 and the 2nd lug groove 12, it inclines and is extended with respect to the tire circumferential direction. However, the angle θ2 of the second connecting groove 22 with respect to the tire circumferential direction is set to be smaller than the angle θ1 of the first connecting groove 21 with respect to the tire circumferential direction.

  The first shoulder block 31 and the second shoulder block 32 are defined by the first lug groove 11, the second lug groove 12, the first connection groove 21, and the second connection groove 22. Since the first shoulder block 31 and the second shoulder block 32 are partitioned by a combination of grooves described later, they are alternately arranged along the tire circumferential direction.

  The first shoulder block 31 is a block defined by the first lug groove 11, the second lug groove 12, and the first connection groove 21. Since it is divided by the combination of the grooves, the inner end portion in the tire width direction of the first shoulder block 31 is disposed closer to the tire equator CL than the inner end portion in the tire width direction of the second shoulder block 32 described later. The first shoulder block 31 includes a transverse groove 31a that traverses each block while being inclined with respect to the tire circumferential direction. In the illustrated example, in addition to the transverse groove 31a, the first shoulder block 31 has a narrow groove 31b positioned on the ground contact end E and extending in the tire width direction, and a tire positioned on the outer side in the tire width direction from the ground contact end E. A narrow groove 31b extending in the width direction and a sipe 31c extending along the longitudinal direction of the first block and intersecting the transverse groove 31a are provided. In the example shown in the figure, a bent portion 31 d is formed at the position of the ground contact E of the first shoulder block 31. Therefore, in the example shown in the drawing, the ground contact end of the first shoulder block 31 itself is located on the inner side in the tire width direction than the ground contact end E (the outer end portion in the tire width direction of the ground contact region).

  The second shoulder block 32 is a block defined by the first lug groove 11, the second lug groove 12, and the second connection groove 22. Since it is divided by the combination of the grooves, the inner end portion in the tire width direction of the second shoulder block 32 is arranged on the outer side in the tire width direction than the inner end portion in the tire width direction of the first shoulder block 31 described above. The second shoulder block 32 includes a transverse groove 32a that crosses each block while being inclined with respect to the tire circumferential direction. In the illustrated example, in addition to the transverse groove 32a, the second shoulder block 32 has a narrow groove 32b extending on the ground contact edge E and extending in the tire width direction, and a tire positioned on the outer side in the tire width direction from the ground contact edge E. A narrow groove 32b extending in the width direction and a sipe 32c extending along the longitudinal direction of the first block and intersecting the transverse groove 32a are provided. In the illustrated example, since the second shoulder block 32 is not formed with the bent portion 31d like the first shoulder block 31, the grounding end of the second shoulder block 32 itself is the grounding end E (the tire width direction outside of the grounding region). Edge).

  In the illustrated example, side blocks 33 are provided outside the first shoulder block 31 and the second shoulder block 32 in the tire width direction. The side block 33 is formed continuously with the first shoulder block 31 and the second shoulder block 32. Therefore, the structure of the shoulder region in the illustrated example is a block (a series of blocks including a first shoulder block 31, a second shoulder block 32, and a side block 33) partitioned between the two first lug grooves 11. It can also be considered that the second lug groove 12 terminating in the block is formed. Since the side block 33 exists in an area where it can sink into mud or the like when traveling in a muddy area, an uneven part 33a is optionally provided as shown in the figure, and mud or the like is bitten into the uneven part 33a. In addition, the mud performance may be improved. In addition, the part shown with the broken line of the uneven | corrugated | grooved part 33a in the figure intends the boundary where a protrusion or a dent starts from the surface of the side block 33 of the uneven | corrugated | grooved part 33a.

  The transverse grooves 31a and 32a formed in the first shoulder block 31 and the second shoulder block 32 both have a bent portion in the middle in the longitudinal direction and have a zigzag shape. One end of the transverse groove 31 a formed in the first shoulder block 31 communicates with the middle part of the first lug groove 11, and the other end communicates with the middle part of the second lug groove 12. One end of the transverse groove 32 a formed in the second shoulder block 32 communicates with the inner end of the second lug groove 12 in the tire width direction, and the other end communicates with the middle part of the first lug groove 11. The transverse grooves 31a and 32a are grooves having a groove width and a groove depth smaller than that of the lug groove and the connecting groove and larger than that of the sipe. Specifically, the groove width of the lug groove is 25 mm to 40 mm, the groove depth is 10 mm to 20 mm, the groove width of the connecting groove is 5 mm to 20 mm, the groove depth is 10 mm to 20 mm, and the groove width of the sipe is While the groove depth is 0.8 mm to 1.5 mm and the groove depth is 2 mm to 15 mm, the groove widths of the transverse grooves 31a and 32a are preferably 2 mm to 5 mm and the groove depth is 5 mm to 10 mm.

  The first lug groove 11, the second lug groove 12, the first connection groove 21, the second connection groove 22, the first shoulder block 31, and the second shoulder block 32 are respectively disposed on both sides of the tire equator CL. The first lug groove 11, the second lug groove 12, the first connection groove 21, the second connection groove 22, the first shoulder block 31, and the second shoulder block 32 located on both sides of the tire equator CL are located on the tire equator CL. The point is substantially point-symmetric with respect to the point.

  Thus, when the first lug groove 11, the second lug groove 12, the first connection groove 21, the second connection groove 22, the first shoulder block 31, and the second shoulder block 32 are provided on both sides of the tire equator CL, Between the first connection grooves 21 positioned on both sides of the tire equator CL, a third connection groove 23 that connects the first connection grooves 21 can be optionally provided. Moreover, the 4th connection groove | channel 24 which connects the 2nd connection grooves 22 can be arbitrarily provided between the 2nd connection grooves 22 located in the both sides of the tire equator CL. In the illustrated example, third connection grooves 23 are formed between the first connection grooves 21 that are point-symmetric with respect to points on the tire equator CL, and are point-symmetric with respect to points on the tire equator CL. Since the third connection grooves 23 are formed between the second connection grooves 22 having the above relationship, the first connection groove 21, the second connection groove 22, the third connection groove 23, and the fourth connection groove 24 are formed. Thus, a plurality of center blocks 34 are defined on the tire equator CL.

  In the present invention, the structure of the shoulder region of the tread portion, that is, the first lug groove 11, the second lug groove 12, the first connection groove 21, the second connection groove 22, the first shoulder block 31, and the second shoulder block 32 is provided. The structure of the first shoulder block 31 and the second shoulder block 32 provided with the transverse grooves 31a and 32a is not particularly limited as to the structure of the center region of the tread portion. For example, without providing the third connection groove 23 and the fourth connection groove 24, it is possible to have a specification in which a rib-like land portion extending continuously in the tire circumferential direction is formed on the tire equator CL.

  As described above, the first lug groove 11, the second lug groove 12, the first connection groove 21, and the second connection groove 22 are provided, and the first shoulder block 31 and the second shoulder block 32 are partitioned by these. Therefore, the mud performance for efficiently discharging the mud in the groove can be improved while the mud etc. are well bitten to obtain excellent traction performance, and the mud performance can be improved. In particular, since the angle of the first connecting groove 21 with respect to the tire circumferential direction is larger than the angle of the second connecting groove 22 with respect to the tire circumferential direction as described above, the traction performance is reduced because it is shorter than the first lug groove 11. The traction performance of the relatively low second lug groove 12 can be supplemented by the first connecting groove 21, and the waste mud of the first lug groove 11 having a relatively low sludge performance because it is longer than the second lug groove 12. The performance can be supplemented by the second connecting groove 22, and the mud performance can be effectively enhanced. On the other hand, the first shoulder block 31 and the second shoulder block 32 are provided with the transverse grooves 31a and 32a, respectively, so that the first shoulder block 31 and the second shoulder block 32 are appropriately divided and between these blocks. Difference in rigidity can be suppressed, and uneven wear resistance can be improved.

  The transverse grooves 31a and 32a can be provided at arbitrary positions of the first shoulder block 31 and the second shoulder block 32, but are preferably arranged at positions where the distance from the outer edge in the tire width direction of each block is the same. It is good to be. Specifically, as shown in FIG. 4, the distance L1 from the outer edge in the tire width direction of the block in the first shoulder block 31 to the innermost point in the tire width direction of the transverse groove 31a, and the second shoulder block 32 It is preferable that the distance L2 from the outer edge in the tire width direction of the block to the innermost point in the tire width direction of the transverse groove 32a satisfies the relationship L1 = L2. In FIG. 4, only the first shoulder block 31 and the second shoulder block 32 and only a part of the side block 33 and the second lug groove 12 are extracted so that the positional relationship between the transverse grooves 31a and 32a becomes clear. Other portions are omitted (part of the cross section of the portion is also indicated by a dotted line). Further, the protrusions 12a in the second lug grooves 12 and the uneven portions 33a formed on the side blocks 33 are also omitted.

  In the example shown in the drawing, the positions of the transverse grooves 31a and 32a in the tire width direction are shifted, but the aforementioned shoulder portion 31d is formed in the first shoulder block 31, and the edge of the first shoulder block 31 (the block is grounded). The end of the block itself) is located on the inner side in the tire width direction than the ground contact E (that is, the edge of the second shoulder block 32), so that the distance L1 and the distance L2 satisfy the relationship L1 = L2. ing. By arranging the transverse grooves 31a and 32a in this way, the rigidity of the outer portion in the tire width direction defined by the transverse grooves 31a and 32a of the first shoulder block 31 and the second shoulder block 32 can be made substantially uniform. This is advantageous for improving uneven wear resistance. At this time, if the distance L1 and the distance L2 do not coincide with each other, the balance of the block rigidity cannot be optimized, and it is difficult to sufficiently enhance the uneven wear resistance.

  In addition, since it is not always necessary to provide the bent portion 31d as in the illustrated example, the positions of the transverse grooves 31a and 32a formed in the first shoulder block 31 and the second shoulder block 32 in the tire width direction are simply set. So that the distance L1 and the distance L2 coincide with each other. Preferably, for example, a bend portion 31d as shown in the figure is provided so that the transverse grooves 31a and 32a formed in the first shoulder block 31 and the second shoulder block 32 are shifted in the tire width direction. Thus, the edge effect (improvement of traction performance) by the transverse grooves 31a and 32a may be exhibited at various portions in the tire width direction.

  As described above, the first lug groove 11 and the second lug groove 12 extend in the tire width direction in the shoulder region of the tread portion, but the angle with respect to the tire circumferential direction at the ground contact end position is 60 ° to 60 ° on the acute angle side. 90 ° is preferred. Specifically, as shown in FIG. 3, the angle (acute angle side) with respect to the tire circumferential direction at the contact end position of the first lug groove 11 is α, and the angle with respect to the tire circumferential direction at the contact end position of the second lug groove 12 ( If the acute angle side is β, these angles α and β are preferably 60 ° to 90 °, respectively. Thus, by setting the angles α and β of each lug groove, the traction performance in the shoulder region can be improved, which is advantageous for improving the mud performance. At this time, if the angles α and β are smaller than 60 °, sufficient traction performance cannot be obtained. The angle α is the tire circumference of the first lug groove 11 at the position of the midpoint of the first lug groove 11 in the tire circumferential direction at the innermost point in the tire width direction of the transverse groove 31a in the first shoulder block 31 and the position of the ground contact E. A straight line connecting the midpoint of the direction is an angle formed with respect to the tire circumferential direction, and the angle β is the tire circumference of the second lug groove 12 at the innermost point in the tire width direction of the transverse groove 32a in the second shoulder block 32. A straight line connecting the midpoint in the direction and the midpoint in the tire circumferential direction of the second lug groove 12 at the position of the ground contact E is an angle formed with respect to the tire circumferential direction.

  The angles θ1 and θ2 of the first connecting groove 21 and the second connecting groove 22 satisfy the relationship θ1> θ2 as described above, but preferably the angle θ1 is set in the range of 45 ° to 90 ° and the angle θ2 is set to 10 It is good to set in the range of ° to 45 °. By setting the angles θ1 and θ2 in this way, the shapes of the first connecting groove 21 and the second connecting groove 22 are optimized, which is advantageous in achieving both uneven wear resistance and mud performance. In the example shown in the drawing, the groove width of the first connecting groove 21 is changed and the second connecting groove 22 is bent. Therefore, the angles θ1 and θ2 are the midpoints at the ends of the grooves as shown in the figure. The angle formed by the connected straight line with respect to the tire circumferential direction.

  As described above, the third connecting groove 23 and the fourth connecting groove 24 are optional elements. Preferably, the third connecting groove 23 and the fourth connecting groove 24 are provided, and a plurality of center blocks 34 are provided on the tire equator CL. It is good to provide. Providing the third connecting groove 23 and the fourth connecting groove 24 in this way is advantageous in improving the mud performance because the traction performance by the third connecting groove 23 and the fourth connecting groove 24 can be secured in the center region.

  When the third connecting groove 23 and the fourth connecting groove 24 are provided, as shown in FIG. 5, the angle θ3 of the third connecting groove 23 with respect to the tire circumferential direction is smaller than the angle θ4 of the fourth connecting groove 24 with respect to the tire circumferential direction. It is preferable. Thus, the third connecting groove 23 and the fourth connecting groove 24 are connected to the first connecting groove 21 having excellent traction performance by making the angles θ3 and θ4 satisfy the relationship θ3 <θ4. Since the traction performance can be improved with respect to the loud connection groove connected to the second connection groove 22 that is excellent in the drainage performance and the second connection groove 22 that is excellent in the drainage performance, the first to fourth connection grooves 24 can be improved. The combination makes it possible to achieve a high level of mud performance.

  The angles θ3 and θ4 of the third connecting groove 23 and the fourth connecting groove 24 can be appropriately set according to the positional relationship between the first connecting groove 21 and the second connecting groove 22 as long as the above-described magnitude relationship is satisfied. Preferably, the angle θ3 is set in the range of 20 ° to 60 °, and the angle θ4 is set in the range of 60 ° to 90 °. By setting the angles θ3 and θ4 in this way, the shape of the groove and block in the center region is optimized, which is advantageous in achieving both uneven wear resistance and mud performance. The angles θ3 and θ4 are angles formed by the center line of each groove with respect to the tire circumferential direction as shown in the figure.

  When the third connecting groove 23 and the fourth connecting groove 24 are provided, the tire equator CL is defined by the first connecting groove 21, the second connecting groove 22, the third connecting groove 23, and the fourth connecting groove 24 as described above. A center block 34 is partitioned on the top, and it is preferable to provide a sipe in the center block 34. In particular, as shown in FIGS. 2 and 5, it is preferable to include a center sipe 34 a extending along the second connecting groove 22. This suppresses the rigidity of the portion of the center block 34 where rigidity is likely to be high because it is located on the extension line of the second lug groove 12 having a short groove length, and blocks near the second lug groove 12 and the second connecting groove 22. The uneven wear resistance can be enhanced by suppressing the difference in rigidity. Moreover, since the edge effect by sipe can be expected, the traction performance can also be improved.

  In the example shown in FIG. 2, sipes are formed in each of the first shoulder block 31, the second shoulder block 32, and the center block 34. In particular, the center sipe 34 a not only extends along the second connecting groove 22 as described above, but also bends in the center block 34 and opens at one end to the first connecting groove 21 and the other end to the second connecting groove 22. It is open. On the other hand, the first shoulder sipe 31c formed in the first shoulder block 31 extends along the second lug groove 12 and opens at a position facing the opening end of the center sipe 34 on the first connecting groove 21 side. The second shoulder sipe 32c formed in the second shoulder block 32 extends along the second lug groove 12 and opens at a position facing the opening end of the center sipe 34 on the second connecting groove 22 side. . Accordingly, when the first shoulder sipe 31c, the second shoulder sipe 32c, and the center sipe 34a are viewed as a series of continuous sipe, this series of sipe (first shoulder sipe 31c, second shoulder sipe 32c, and center sipe 34a). Is arranged so as to surround the second lug groove 12. By providing the first shoulder block 31, the second shoulder block 32, and the center block 34 in this way, the balance of the block rigidity particularly around the second lug groove 12 can be improved, so that uneven wear resistance is improved. It is advantageous to increase. Moreover, since the edge effect by these sipes can be expected, it is advantageous for improving the traction performance.

  The tire size is LT265 / 70R17, has the basic structure illustrated in FIG. 1, is based on the tread pattern of FIG. 2, and has a relationship between the angles of the first and second connection grooves (first / second connection). Groove angle), transverse groove position, angle α with respect to the tire circumferential direction at the contact end position of the first lug groove, angle β with respect to the tire circumferential direction at the contact end position of the second lug groove, third connection groove and fourth connection The presence / absence of a groove (the presence / absence of a third / fourth connecting groove), the relationship between the angle θ3 of the third connecting groove with respect to the tire circumferential direction and the angle θ4 of the fourth connecting groove with respect to the tire circumferential direction (the third / fourth connecting groove Angle) and nine types of pneumatic tires of Conventional Example 1, Comparative Example 1, and Examples 1 to 7 in which the presence or absence of a center sipe was set as shown in Table 1 were prepared.

  In any example, as illustrated, the first lug groove is longer than the second lug groove, and the first lug groove and the second lug groove are alternately arranged in the tire circumferential direction. A transverse groove is formed in both the first lug groove and the second lug groove.

  The column of “crossing groove position” in Table 1 indicates whether or not the distances L1 and L2 from the edge of each block where the crossing groove is formed to the crossing groove match. Specifically, “L1 = L2” means that the distance from the edge of each block in which the transverse groove is formed to the transverse groove coincides, and “L1 ≠ L2” means that each transverse groove is formed. This means that the distance from the edge of the block to the transverse groove varies from block to block.

  These nine types of pneumatic tires were evaluated for mud performance and uneven wear resistance performance by the following evaluation methods, and the results are also shown in Table 1.

Mud performance Each test tire was assembled on a wheel having a rim size of 17 × 8.0, mounted on a pickup truck (test vehicle) with an air pressure of 450 kPa, and sensory evaluation of traction performance by a test driver was performed on a muddy road surface. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. A larger index value means better mud performance.

Uneven wear resistance performance Each test tire was assembled to a wheel with a rim size of 17 x 8.0, mounted on a pickup truck (test vehicle) with an air pressure of 450 kPa, and after running 20000 km on a dry road surface, uneven wear (heel and wear) The amount of wear was measured. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. The larger the index value, the smaller the wear amount and the better the uneven wear resistance.

  As is clear from Table 1, each of Examples 1 to 8 improved the mud performance and uneven wear resistance compared to Conventional Example 1, and balanced these performances in a well-balanced manner. As can be seen from Examples 1 to 5, Examples 1, 4 and 5 in which the positions and angles α and β of the transverse grooves are set appropriately are excellent in greatly improving the mud performance and uneven wear resistance. Showed performance. Further, as can be seen from the comparison between Example 1 and Examples 6 to 8, sufficient effects were obtained in Example 6 having no third connection groove, fourth connection groove, or center sipe. By providing the connecting groove, the fourth connecting groove, and the center sipe to make them preferable modes, a more excellent effect was obtained.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 11 1st lug groove 11a Protrusion part 12 2nd lug groove 12a Protrusion part 21 1st connection groove 22 2nd connection Groove 23 Third connection groove 24 Fourth connection groove 31 First shoulder block 31a Transverse groove 31b Narrow groove 31c Sipe (first shoulder sipe)
31d Bending part 32 Second shoulder block 32a Transverse groove 32b Narrow groove 32c Sipe (second shoulder sipe)
33 Side block 33a Concavity and convexity 34 Center block 34a Sipe (center sipe)
CL tire equator E Grounding end

Claims (8)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the provided pneumatic tire,
It has a plurality of first lug grooves extending in the tire width direction in the shoulder region of the tread portion and a plurality of second lug grooves shorter than the first lug grooves, and these first lug grooves and second lugs Grooves are alternately arranged along the tire circumferential direction, and the first lag groove extends from the front end of the first lug groove to the second lug groove and from the front end of the second lug groove. A second connection groove extending to the tire, the angle of the first connection groove with respect to the tire circumferential direction is larger than the angle of the second connection groove with respect to the tire circumferential direction, and the first lug groove, A plurality of first shoulder blocks are defined by the second lug groove and the first connection groove, and a plurality of second shoulder blocks are defined by the first lug groove, the second lug groove, and the second connection groove. The tire of the first shoulder block The inner end in the direction is disposed closer to the tire equator than the inner end in the tire width direction of the second shoulder block, and each of the first shoulder block and the second shoulder block is inclined with respect to the tire circumferential direction. A pneumatic tire comprising a transverse groove that crosses the tire.   2. The air according to claim 1, wherein the transverse groove is arranged at a position where the distance from the outer edge in the tire width direction of each block is the same in the first shoulder block and the second shoulder block. Enter tire.   The first shoulder block has a neck portion at a ground contact end position, and an outer edge in the tire width direction of the first shoulder block is located on an inner side in the tire width direction than the ground contact end position. Item 3. The pneumatic tire according to Item 2.   The air according to any one of claims 1 to 3, wherein an angle of the first lug groove and the second lug groove with respect to a tire circumferential direction at a contact end position is 60 ° to 90 ° on an acute angle side, respectively. Enter tire.   A plurality of third connection grooves that connect the first connection grooves located on both sides of the tire equator and a plurality of fourth connection grooves that connect the second connection grooves located on both sides of the tire equator; A plurality of center blocks are defined on the tire equator by the first connection groove, the second connection groove, the third connection groove, and the fourth connection groove. The pneumatic tire according to Crab.   The pneumatic tire according to claim 5, wherein an angle of the third connection groove with respect to the tire circumferential direction is smaller than an angle of the fourth connection groove with respect to the tire circumferential direction.   The pneumatic tire according to claim 5 or 6, wherein the center block includes a center sipe extending along the second connection groove.   The first shoulder block includes a first shoulder sipe extending along the second lug groove, the second shoulder block includes a second shoulder sipe extending along the second lug groove, the center sipe, the first The pneumatic tire according to claim 7, wherein the one shoulder sipe and the second shoulder sipe are arranged so as to surround the second lug groove as a series of sipes.

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